I hated my two terms of electronics classes. (It's the physics-major equivalent of circuits, since all we did was do theory on them during lecture and then spend six hours a week - or more - building them in the lab.) My prof couldn't teach, the TA was lazy and biased against girls, and he introduced us to complex notation before we'd done much with it in other classes. I spent upwards of 20 hours a week on those classes, between doing stuff in the lab and writing up reports. This would be why people back off when they see my expression after they mention circuits. *wink*
Calculus isn't bad once you get a lot of experience with it. The theory sucks; the application is worthwhile. Well, as long as you don't get a bunch of square roots in the denominator of a multi-dimensional integral, that is. Those are cruel.
Differential equations are quickly becoming important to me, since that's all I've been doing this term in classical mechanics. (You think Newton's the definitive answer to classical stuff? It's not true, unfortunately. It's absolutely frightening how much further the math can go...)